Capillary devices for determination of surface characteristics and contact angles and methods for using same

ABSTRACT

Devices are presented which allow determination of unknown surface properties through the creation of a channel capillary, comprised in part of the subject surface or surfaces, and measurement of the capillary pressure created by a test fluid within the resultant channel. In various embodiments of the invention, a channel is created in a reference material which is bonded, through some mechanism, to the test surface in order to create a narrow capillary channel. In other embodiments of the invention, the capillary channel is created with test surfaces on either side of standoff strips which space the surfaces a precise distance from one another. Methods are presented for using these capillaries through immersion, along their length, in a bath of test fluid, such that the resultant fluid level provides a measure of capillary pressure. Being, in part, a consequence of the contact angle between the test fluid and the surface or surfaces under consideration, the capillary pressure is a convenient measure of surface properties inherently related to printability, affinity for adhesives, surface contamination by foreign substances, surface roughness, and the like. Devices are presented which allow measurement of test fluid height within the capillary, both in situations where a static equilibrium is achieved, and in situations where a dynamic contact angle is operative as the fluid rises or falls within the capillary.

RELATED APPLICATIONS

[0001] The present application is based on and claims priority to aprovisional application having U.S. Serial No. 60/424,124 filed on Nov.6, 2002.

BACKGROUND AND FIELD OF THE INVENTION

[0002] In a wide range of scientific, industrial, and medicalapplications, direct or inferential measurements of the contact anglebetween a free liquid surface and a solid interface are of greatpractical importance and value. Given the contact angle at a givenliquid-solid interface, it is often possible to utilize known empiricallaws to understand and predict a wide range of related physicalphenomena. Specifically, the interfacial contact angle, along with fluidproperties such as surface tension, viscosity, and density, enablemodeling of processes including surface wetting, wicking in pores, andcapillary pressure, to name a few. In addition, since the contact anglebetween a given fluid and surface bears important information regardingaffinity for other materials, surface roughness, molecular surfacemorphology, and the like, any related measurement can prove useful inrelative comparisons of surface properties.

[0003] Among the many important uses of contact angle data, oneparticularly common and valuable application involves measurements whichprovide a relative ranking of how substances will print, bond, or adhereon a given surface. As is well known, surfaces often display varyingdegrees of affinity for substances which may be fused or bonded to them.Many polymer surfaces, for example, display a general lack of affinityfor other materials and are inherently difficult to fuse, bond, adhere,or print with other substances. In such cases, a variety of treatmentsor coatings are often applied to alter surface compatibility. Measuresof surface properties which correlate with the affinity of a givensurface to other materials is of value in related enterprises. Contactangle measurements are commonly used for this purpose (to control andgage the effectiveness or surface treatments, for example) since theyare known to correlate with surface affinity for other substances andrelative compatibility. Various less direct measurements, whichcorrelate to contact angles in some way, find similar use in ranking andcomparing the properties of surfaces as they relate to printing,bonding, and adherence with other materials.

[0004] Given the vast utility of contact angle measurements, rangingfrom basic research to practical analysis of printability, themeasurement of contact angles has been the subject of extensiveinvestigation, development, and invention. At present, a number oftechniques for the measurement of contact angle between a given fluidand surface are well known, and devices are commercially available whichutilize these techniques to provide related measurements.

[0005] Among the most straightforward of techniques for measurement ofcontact angles involves the placement of a test droplet on a subjectsurface and direct observation using optical magnification. The contactangle at the edges of the drop is, thus, directly observed and measured.A wide range of commercial devices currently offer this capabilityincluding instruments manufactured by Dataphysics Instruments, GmbH ofFilderstadt, Germany, Kernco Instruments co., Inc. of El Paso, Tex., andAST Products, Inc. of Bilerica, Mass..

[0006] Another technique involves mounting a subject surface on afixture which is attached to a microbalance. The surface is thensuspended within a test fluid and resulting forces are measured. Afterproperly accounting for buoyant forces, and sample geometries, it ispossible to deduce contact angle information from such measurements. Inaddition, it is possible to measure the angle dynamically, as the fluidsurface either advances or recedes over the surface, and utilize thisdata to compute advancing or receding contact angle. Instruments whichperform this type of analysis, thus, provide sophisticated dynamiccontact able measurements for innumerable applications ranging frombasic research to analysis of bonding and adherence. Any number ofanalytical instruments of this type are currently available commerciallyincluding those manufactured by Kruss, GmbH, Dataphysics Instruments,GmbH of Filderstadt, Germany, and AST Products, Inc. of Bilerica, Mass..

[0007] The commercial interest in such instrumentation, and the vastutility of the information they provide, has driven tremendousdevelopment in this general area. Examples of developments in themeasurement of contact angles and related surface properties areexemplified by U.S. Pat. Nos. 4,050,822, 5080,484, and 5,268,733 whichare incorporated herein for reference. U.S. Pat. No. 4,050,822 describesa device which dispenses a droplet of known volume onto a test surface,and allows inference of the fluid contact angle from the measuredmaximum droplet height above the interface. U.S. Pat. No. 5,080,484describes a device for measuring the contact angle through themeasurement of laser light reflected from the liquid and solid surfacesalong a line of contact. U.S. Pat. No. 5,268,733 describes a devicewhich enables determination of contact angle through projection of theimage of a droplet onto a screen, and use of a special protractor scalefacilitating accurate determination of contact angle.

[0008] Although this prior art is sophisticated, and enables accuratedetermination of contact angles and related information for manyapplications, associated instrumentation is typically complex andexpensive. Although this level of sophistication fills an importantneed, there is considerable demand for measurement techniques moresuited to immediate analysis of surface characteristics in routineanalysis. Particularly in manufacturing settings, where quality controlmetrics are needed for surfaces, but analysis must be carried outquickly and with minimal complexity, there is a need for improvedmethods. In addition, there is a constant demand for advancement in thisgeneral area of surface analysis, and any technique which offersalternatives to current methodology and instrumentation holds thepotential to dramatically extend and augment current measurementcapabilities.

[0009] One alternative which currently exists for immediate grossindications of surface bondability and printability is provided byexamination of wetting by a series of different fluids. So-called dynetest fluids are engineered with a range of different surface tensions.These fluids are progressively swabbed or smeared on to a subjectsurface (sometimes with a specially designed pen), to determine thosewhich bead and those which wet. Although this is not a direct measure ofcontact angle for any specific fluid on the surface, the surface tensionof the fluid which will wet the surface is generally correlated with thecontact angle of a given specific fluid. In addition, the result issimilarly correlated with affinity for inks and other substances. U.S.Pat. No. 4,694,685, which is incorporated herein for reference, presentsa set of water-based fluids with different surface energies but whichare nearly identical in other respects (such as viscosity). In addition,Diversified Enterprises-ADT of Claremont, N.H., U.V. Process Supply Inc.of Chicago, Ill., and Vetaphone of Kolding, Denmark, all offer dyne testfluids or dyne test pens for use in the manner described.

[0010] Although dyne test fluids are a pragmatic and immediate means fordetermining surface properties, they provide only a gross and somewhatsubjective measurement. In addition, contamination of the fluids,toxicity, and perishibility can present a host of issues in practicalapplication.

[0011] For all of these reasons, there is a need for methods and deviceswhich augment those currently available for the measurement of contactangles and related information. Where such methods and devices offerextensions of the more sophisticated aspects of current technology, theypromise to extend the scope of current measurement capabilities. While,in itself, the value of such extension is clear, there is a further needfor any technology which enables simple, cost effective, and accuratemeasurement of surface properties in routine applications such asquality control.

SUMMARY OF THE INVENTION

[0012] It is one feature of the present invention to provide a simpleand practical means of measuring surface properties and static contactangles between fluids and a test surface through incorporation within acapillary and measurement of capillary pressure. It is a further featureof the present invention to provide devices and techniques forincorporation of a test surface within a capillary and subsequentmeasurement of capillary pressure as the fluid advances or recedes toyield a new analytical technique for measurement of dynamic contactangles.

[0013] The instant invention, in one embodiment, is generally directedto a device which incorporates the surface or surfaces to be testedwithin a capillary of known dimensions. The capillary thus created isintended for submersion within a bath of fluid such that the height towhich the fluid rises in the capillary, relative to the surface of thefluid within the vessel, may be measured. The fluid height is a measureof capillary pressure and, given the geometry and composition of thecapillary, allows calculation of contact angle and inference of relatedproperties.

[0014] Versions of this invention may be augmented with an apparatuswhich enables the surface of the fluid bath to move relative to thecapillary, causing the fluid level within the capillary to rise or fallat a given rate. Through measurement of the relative height between thelevel of fluid in the bath and the height of fluid in the capillary, adynamic measure of capillary pressure is thus obtained. Just as in thestatic case, this dynamic pressure may be used to calculate the contactangle with the unknown surface under dynamic conditions, the resultbeing the dynamic contact angle at a given rate of advancement orrecession.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 shows a rectangular reference channel, A, within thesurface, B, of a supporting material, C.

[0016]FIG. 2 shows a rectangular reference channel, A, covered by amaterial for testing, B, to form a channel capillary device, C.

[0017]FIG. 3 shows a container, A, in which a channel capillary device,B, is suspended in a bath of reference fluid C. The fluid column withinthe capillary, D, rises to some height relative to the bath surface, E.

[0018]FIG. 4 is a magnified schematic view (not to scale) of the fluidcolumn within a reference channel cavity device. A materials system, A,supports a reference channel, B, which is sealed against a material fortesting, C. This forms a closed capillary into which fluid will rise orfall. The fluid contact angle against the reference channel, D, causesthe fluid to push downwards (or upwards) along the line of contact, F.The fluid contact angle against the subject surface, E, causes the fluidto pull downwards (or push upwards), along the line of contact betweenthe fluid and that surface, G. These forces cause the fluid to rise (orfall) some level above (or below) the fluid bath surface, H.

[0019]FIG. 5 shows a curved reference capillary device for the testingof curved surfaces. In the figure, a reference channel, A, is embeddedwithin a curved surface in order to allow testing of a curved subjectsurface, B.

[0020]FIG. 6 shows a reference channel capillary device wherein areference channel, A, embedded within the flat surface of a material, C,is covered on its upper surfaces, excluding the reference channel, witha pressure sensitive adhesive, B.

[0021]FIG. 7 shows a reference channel capillary device wherein areference channel, A, embedded within the flat surface of a material, C,is covered on its upper surfaces, excluding the reference channel, witha pressure sensitive adhesive, D. The subject surface of a plate, B, isbonded to the pressure sensitive adhesive to form a closed capillarywhich is ready for submersion and testing.

[0022]FIG. 8 shows a spacer wall capillary device wherein the flexiblespacer walls, A, are applied to a subject surface, B, while held attheir ends by tabs, C. This spacer system is easily created by cutting arectangular section from a strip, D.

[0023]FIG. 9 shows a system for causing fluid to advance within acapillary device. Fluid is pumped, at a given rate, into a vessel, A,through the tube B. This causes the surface of the fluid, C, to rise.The resultant column of fluid within the capillary, D, will, thus, riseto create dynamic advancement of the fluid interface at the capillarywalls.

[0024]FIG. 10 shows a system for causing fluid to advance or recedewithin a capillary device. Within a vessel, A, a mechanical stage, B, iscaused to move up, or down, relative to the surface of the test bath, C.The column of fluid within the capillary will, thus, advance or recedeover the capillary walls to enable dynamic measurements.

[0025]FIG. 11 shows a schematic of a mold used to cast a referencechannel device. The mold may be constructed from a block of 17-4stainless steel, A. The width of the mold, B, may be 0.8 inches, thelength, C, may be 8.0 inches, and the height, D, may be 2.0 inches inone embodiment. A step on one of the long sides of this block, E, may bemachined to a height of 0.015 inches and a width of 0.150 inches.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Embodiments of the instant invention serve to create capillarieswhich enable measurement of the pressure produced by the surface tensionof a test fluid and the contact angles it presents at the capillarywalls. As one example of this concept, it is illustrative to consider adevice including a rectangular reference channel, of known depth andwidth, within a reference material as shown in FIG. 1. If a surface ofunknown characteristics is sealed, through clamping, adhesion, or anyother mechanism over this channel, as shown in FIG. 2, the result is achannel capillary, one internal surface of which is the surface to betested. Upon submersion along its length to some depth within a testfluid, the fluid will rise in the capillary until hydrostatic pressureis balanced by capillary pressure, as shown in FIG. 3. Since thecapillary pressure is a consequence of fluid surface tension, andcontact angles at the capillary walls, the height of fluid within thecapillary is intimately related to these parameters. With properanalysis, fluid height measurements may be used to infer the fluidcontact angle with the surface being tested, or simply as a measure ofsurface properties.

[0027] Referring to FIG. 4, it is possible to infer the contact angle ofthe fluid with the test surface through consideration of the exactconditions which exist at the fluid interface in equilibrium. Assumingthat the surface tension of the test fluid is given by y, and that thefluid makes a contact angle of θ_(known) with the surfaces of thereference channel, the surface tension, pulling at the line of contactacross the width of the reference channel, exerts a downward force of

F=yw cos(θ_(known)),

[0028] Where y is the fluid surface tension, w, is the channel width andθ_(known) is the fluid contact angle with the reference surface.

[0029] Similarly, the surface tension of the fluid, pulling at the lineof contact across the width of the test surface within the capillary,exerts a downward force of

F=yw cos(θ_(known))

[0030] on the column of water (where θ_(unknown) is the fluid contactangle with the subject surface). These forces combine to yield a totalresultant force of

F _(total) =yw(cos θ_(known)+cos θ_(unknown)).

[0031] While the two sides of the capillary along its depth alsocontribute to the total force on the column due to fluid surfacetension, these forces may be ignored provided that the depth of thechannel is small in comparison to its width. Given this approximation,the capillary pressure may be calculated by considering that the totalforce acts on a surface with the cross sectional area of the channel,

A=wd,

[0032] (where d is the channel depth) to produce an effective capillarypressure of

P _(capillary) =y/d(cos θ_(known)+cos θ_(unknown)).

[0033] In static equilibrium, this pressure must be equal to thehydrostatic pressure within the fluid at the surface of the fluid withinthe capillary. Hydrostatic pressure, produced by the action of gravityon the fluid, is given by

P _(hydrostatic) =ρgh

[0034] where ρ is the fluid density, g is the acceleration due togravity, and h is height of the fluid within the capillary above orbelow the surface of the fluid bath. Equating the hydrostatic andcapillary pressures, and solution for the contact angle between thefluid and test surface yields:

θ_(unknown)=cos⁻¹(ρghd/y−cos θ_(known)).

[0035] Given the various fluid properties and θ_(known), therefore, itis possible to determine the contact angle of the fluid with the testsurface.

[0036] As one of ordinary skill in the art will recognize, any number ofmethods may be used to determine θ_(known). Probably the moststraightforward technique involves measurement of the height of fluidwithin the capillary using a test surface identical to the referencechannel. In this case, θ_(known) is given by

θ_(known)=cos⁻¹(ρghd/2y).

[0037] In addition, two reference channels may be created with differentknown depths to provide two measurements of fluid height against thesame test surface. This gives simultaneous equations in θ_(known) andθ_(unknown) which may be solved for each.

[0038] Given this analysis, it is clear that the height to which fluidwill rise in a capillary device, designed to incorporate a subjectsurface, is intimately related to the manner in which the fluidinteracts with that surface, and the associated contact angle. Whilesuch analysis serves to demonstrate important principles, most notablyan intimate relationship between measurements enabled by the inventionand subject surface properties, the analysis is based purely on amathematical model with associated approximations and limitations. Itis, thus, offered only to facilitate understanding of the linkagebetween measurements provided by the invention and subject surfaceproperties. While such an analysis, with more or less sophistication,may be utilized to examine physical properties of a surface inconnection with measurements provided by the invention, no aspect ofsuch an analysis is essential for many practical applications.Certainly, it is possible to utilize measurements provided by theinvention in any number of other more and less sophisticated forms ofanalysis. In particular, it is possible to simply utilize the devices ofthe present invention to compare the empirical measurement of fluidheights obtained with different subject surfaces. Further, it ispossible in the any manner of more in depth theoretical and or empiricalanalyses including the verification and study of mathematical modelssuch as the one presented.

[0039] Turning to actual embodiments of the invention, there is noconstraint that the reference channel possess a rectangular crosssection. While a rectangular channel is advantageous for simplicity incontact angle calculations, devices with a wide range of different crosssectional shapes are viable and represent embodiments of the presentinvention. Specifically, semicircular, semiovular, triangular, andnearly any other form which allows incorporation of the test channelwithin the capillary, are all viable embodiments. Results obtained usingsuch a system may be used either comparatively (through comparison ofresults obtained using different surfaces) or quantitatively throughappropriate calculation of the contact angle, just as outlined above fora rectangular channel. In some cases, associated calculations may becarried out using computer based numerical methods.

[0040] As one of ordinary skill in the art will further recognize, thesubject surface may not be planar. In many circumstances, for example,it is desirable to measure the surface properties of plastic bottles,and other articles, which have been molded and surface treated. In suchcircumstances, the capillary device may be constructed to allowconformation over the contour of the surface. An example of such adevice, with a form suitable for testing a surface with cylindricallysymmetric geometry, is shown in FIG. 5. Provided the radius of curvatureof such a surface is large in comparison to the ultimate capillarydepth, capillary pressure is little influenced by associated effects,and the mathematical analysis above may be used for analyticaldetermination of contact angle to within a good approximation. Even incases where the curvature causes a significant effect, a very similarmathematical analysis may be undertaken and utilized in associatedanalysis.

[0041] Dimensions of useful embodiments of these capillary devices mayvary considerably. For most applications, the reference channel shouldbe practical to fabricate with high precision, but also appropriate toproduce strong differential fluid height changes in response todifferences in test surface characteristics. As one example, ordinarymold machining tolerances, will allow construction of rectangularchannels within a tolerance of +−0.0005 inches, while greater accuracycan prove impractical for any number of reasons. In rectangularcapillaries, since the height of the fluid within the capillary isroughly inversely proportional to the depth of the cavity, an error inreference channel depth will, approximately, correspond to aproportional error in estimation of the cosine of fluid contact anglewith the reference surface. A reference channel 0.005 inches in depth,therefore, could be expected to cause an error in determination ofcos(θ_(unknown)) by as much as +−10 percent, given typical fabricationlimitations. It is, therefore, typical to arrange the capillary depthsuch that fabrication tolerances yield acceptable results. In general,channels having a depth around 0.015 inches are optimal for manypractical applications since this depth yields a strong fluid heightchange across the range of test surfaces typically encountered (on theorder of greater than 1 inch of possible range).

[0042] The width of a reference channel may also vary over a wide range.It is important to recognize, however, that analysis may be simplified,and sensitivity improved, if the width of the channel is large incomparison to its maximum depth. In channels of rectangular crosssection, for example, the fluid in contact with the side walls of thechannel will contribute to the forces acting on the fluid column (whichare not a consequence of interaction with the test surface underconsideration). In theoretical analysis of capillary pressure,computations are simplified if these side wall forces, and the effectsat the wall corners, can be ignored to within a reasonableapproximation. Such an approximation, as incorporated into thetheoretical analysis presented above, is appropriate if the capillarywidth is large in comparison to its depth. Provided the ratio of thecapillary width to its depth is approximately 10 or greater, theresultant error in calculation of forces is on the order of 10 percentor less, leading to generally acceptable results.

[0043] Although channels of great width are desirable, given theconsiderations above, other factors can limit the utility of channels ofvery great width. Most importantly, as the channel width becomes verylarge, relative to the channel depth, mechanical rigidity of the devicecan become a serious concern. Since even a slight deformation of a fewthousandths of an inch can lead to results biased by a substantialerror, it is typically desirable for the channel to be self supportiveduring use, and that undo variations in capillary depth not result frommechanical deformation under the action of stresses created by thefluid, and support of the device during use. While some materials ofconstruction are sufficiently rigid to prevent such deformation, and thereference channel may be fabricated within a thickness of materialsufficient to minimize deformation effects, it is typically desirable tolimit the width of the channel for the sake of rigidity and mechanicalstability. Preferably, it is desirable for the channel width to be lessthan 1000 times the maximum channel depth. More preferably, the channelwidth is less than 100 times the channel width and, most preferably, thechannel width is less than 20 times the channel width.

[0044] While these general geometrical guidelines are provided for thesake of understanding and illustration, they are in no way intended tolimit the scope of the present invention. In any number of specialcircumstances, the height of a reference channel may be arranged toprovide a large signal and be extremely small (perhaps under 0.001inch). In addition, there are circumstances where the channel depthcould be quite large to facilitate great relative accuracy in channeldimensions while producing a small, but measurable, height differencefor different surfaces.

[0045] Given these fundamental concepts and geometrical considerations,embodiments of the capillary devices associated with the invention mustalso facilitate the incorporation of a subject surface into one or morewalls of a capillary with known geometry. For instance, two distinctpractical embodiments of such a device are as follows. In the first, anopen reference channel, having a cross-sectional profile of arbitrary,but known, form, may be embedded within the surface of a material suchthat the subject surface may be sealed on top to create an appropriatecapillary. Herein, such a device will be referred to as an open channeldevice. Secondly, the device may include two spacers, of a giventhickness, which may be sealed between two surfaces (at least one ofwhich is the subject surface), to create a channel capillary of knownthickness. Herein, such a device will be henceforth referred to as aspacer wall capillary device.

[0046] The materials of construction for practical embodiments of openchannel devices can vary according to the exact needs of a specificapplication and may include a variety of composite or laminatestructures. It is possible, for example, to fabricate a referencechannel device into the surface of a plate of glass. Coating of theglass surface (exclusive of the reference channel) with a pressuresensitive adhesive, as shown in FIG. 6, allows convenient attachment ofa subject surface as shown in FIG. 7. It is also possible to constructreference channel devices into the surface of various polymer plates,tapes, etc. and to attach the subject surface using pressure sensitiveadhesives or the intrinsic adherent properties of a given base material.Nearly any base material is suitable, provided it offers sufficientmechanical stability, does not dissolve, react, or otherwise interact insome undesired fashion with the test fluid, and may be bonded, throughsome mechanism, to subject surfaces.

[0047] Specific materials of construction for reference channel devicescan be selected from many different substances, depending on the desiredmechanism for attachment of the subject surface, test fluid properties,etc. Provided a means of attachment (which may include adhesives,mechanical attachment, or any form of bonding appropriate to seal thesubject surface over the reference channel) reference channel devicesmay be constructed of metal, glass, ceramic, semiconducting, or polymerbase materials. Metals may include, but are not limited to, stainlesssteels, carbon steels, aluminum, brass, titanium, platinum, gold,copper, lead, graphite or other carbon morphologies, silver, bronze, andlow melting alloys such as various grades of solder.

[0048] Various grades of glass may be employed including, but notlimited to, borosilicate formulations, fused silica, and the like.Ceramics and related composites base materials may include, but are notlimited to, silicon carbide based composites, silica-alumina composites,zeolites, clays, and the like. Semiconducting materials such as siliconin particular, and doped or coated similar semiconductors, may furtherbe employed as a material base. Finally, polymers suitable for use asbase materials may include, but are in no way limited to, PTFE,co-polymers with TFE, fluopolymers and rubbers, LDPE, HDPE, PET, PPE,PS, PC, Polyamides, Polimides, Thermoplastic Elastomers (including SIS,SEBS, Polyether-esters, or any other block copolymer TPE formulation),Thermoplastic Polyurethanes, Vulcanized rubbers (including polyisoprenerubber, latex rubber, silicone rubber, and polyurethane), and the like.

[0049] The surface of the reference channel in such devices, which makescontact with the test fluid, may simply be the exposed surface of thesupporting material. Many other constructs are also useful, however,including a reference channel formed within a suitable supportingmaterial such as glass, but which is coated with a second material.Using this technique, a wide range of coatings are possible which mayoffer different contact angles with water, different chemical properties(for exposure to different fluids), etc. Coatings may comprise, but arein no way limited to, polymers applied through solvent, aqueous, ordispersion methods, silanes, thermoplastic and thermosetting materials,etc. Where polymer substrates are used, surface treatments such as flametreatment, corona treatment, plasma treatment, or chemical deposition ofa thin layer of metal, or other material, may be utilized to create adesired surface. Finally, particularly where glass, ceramic, metal, orsemiconductor surfaces are employed, all manner of coatings, appliedthrough chemical vapor deposition, vacuum evaporation, sputtering, etc.may be utilized.

[0050] In the design of a specific reference channel device, the opticalclarity of base materials and coatings can be an importantconsideration, depending on the optical properties of the subjectsurface/material and the desired method for measuring the fluid columnheight during use. Where the fluid height must be measured throughdirect optical observation of fluid height, it is necessary for eitherthe subject interface, or the reference channel device itself, to besufficiently clear to allow such observation. In cases where the subjectsurface/material does not facilitate visual or optical observation offluid within the capillary, it is necessary to construct the referencechannel device of materials which are sufficiently transparent, andusing techniques which produce surfaces sufficiently smooth to allowthrough observation. Certainly, constraints on optical clarity can bealleviated through incorporation into the capillary device some meansfor measuring fluid height within without the requirement for directobservation. Such means can include, but are not limited to, sensing ofelectrical resistance or impedance of the fluid column, sensing ofelectrical resistance or impedance of a film coated within the referencechannel, acoustic sensing of the fluid height, etc.

[0051] For general application in many practical scenarios, such astesting of polymer films to determine printability and the like, it isdesirable for reference channel devices to be fabricated in the surfaceof a flexible, clear, strip of material which will adhere to smoothsurfaces. In one embodiment, we have found that highly plasticizedthermoplastic elastomers, including styrene ethylene-butylene styrene(SEBS) rubbers plasticized with mineral oil, are particularly wellsuited to this purpose. Specifically, mineral oil plasticized SEBSrubbers may be molded, through various techniques, to produce a teststrip, containing a reference channel, which will lightly adhere to asubject surface owing to the natural adherent character of such rubbers.Being translucent to extremely clear, test strips comprised of suchmaterials are easily attached to a subject surface and submersed inwater to obtain quick results.

[0052] Oil plasticized SEBS rubbers suitable for use in the fabricationof such test strips range in hardness from a Shore A of greater than 30to those with extreme plasticazation producing hardness valuesimmeasurable on the Shore A scale. Polymers suitable for use in suchformulations include, but are not limited to, the Kraton G series ofthermoplastic elastomers. These polymers may be plasticized in the rangefrom about 50 percent by weight oil to in excess of 90 percent by weightoil. As is common practice with block co-polymer thermoplasticelastomers which physically crosslink due to stryrenic end blocks, awide range of oils with low aromatic content are appropriate for use inthese formulations. The entire DP series of oils, manufactured byLyondell lubricants, Inc., for example, are well suited for formulationof specific embodiments.

[0053] Specific formulations of thermoplastic elastomers, useful inreference channel devices, may incorporate, beyond the base polymer andplasticizer, minor components which modify mechanical and surfaceproperties as desired. The incorporation of parafin wax, for example, isuseful in modifying the surface properties of a test strip to render itmore hydrophobic and, in some cases, improve other attributes whichinfluence the utility of resulting capillary measurements.

[0054] As is commonly recognized, the contact angle between a specificfluid and a solid surface is often dependent upon the rate at which thefluid front advances or recedes over that surface. In addition, a widerange of related phenomena are possible and, in some cases, result inapparent changes in contact angle over time in given system. The contactangle at the edges of a sesile drop of fluid placed on a solid surfacecan, for example, drift dramatically over time due to a variety ofdynamic effects. If such effects occur at the surfaces of a referencechannel device, or at the surface of the material being tested, theheight of fluid within the capillary will be observed to be dynamic. Infact, such effects are almost always present to some degree. If purely aconsequence of the reference channel surfaces, however, and ofsignificant magnitude and duration, these effects can limit the utilityof the device or dictate analysis of the dynamics in order to determinecontact angle as a function of time, or some related normalization.

[0055] For this practical reason, it is often desirable for referencechannel surfaces to display minimal contact angle dynamics, or dynamicswhich die away quickly, allowing immediate achievement of a staticcondition. When employing SEBS rubbers to construct the referencechannel, a wide range of additives may influence the dynamics of contactangle at their surface, making optimization of formulation desirable.While the range of possible additives is extremely large, and any numberof related optimizations are feasible, we have found that the additionof parafin wax tends to minimize contact angle dynamics within a givenoil plasticized SEBS formulation. In concentrations ranging from about 1percent by weight to about 10 percent by weight (as a percentage ofoverall formulation weight), the addition of wax tends to minimize theeffect of contact angle dynamics, improving characteristics of resultingcapillary devices.

[0056] A wide range of manufacturing techniques may be used to producereference channel devices. In general such methods are dictated by thematerials of construction and simply must be appropriate to produce thedesired capillary structure within the base substance. In the case ofmany metals, plastics, some ceramics, and even glass (with diamondtooling), general machining techniques may be employed including CNCbased methods. For metals, electrical discharge machining may beutilized. Etching and related chemical processes may be similarlyemployed, given a base material which may be removed through somechemical or electrochemical process. In the case of materials which maybe processed in molten or liquid form, such as plastics, a very widerange of molding methods may be used including, but not limited to,injection molding, centrifugal molding, blow molding, and molten orsolvent casting. Finally, continuous processes may be employed toproduce embodiments of the invention such as extrusion casting onto aroll with the reverse image of the desired capillary therein, orcalendering or calendering to continuously impress a reference channelwithin sheet, film, or tape stock of metal or polymer which may besubsequently cut into individual strips of a given length.

[0057] In spacer wall embodiments of the present invention, somewhatgreater flexibility in the materials of construction may be possible. Ingeneral, this specific embodiment only requires that materials ofconstruction space the working surfaces within the capillary anappropriate distance apart, seal against the face of these surfaces, andnot solvate in or contaminate the test fluid in any manner. For thisreason, it is generally possible to construct such a device from nearlyany material which may be fashioned to precisely produce an appropriatespacer wall and, through some mechanism, may be bonded to the workingsurfaces in order to form a capillary. Preferably, such devices areconstructed of metal, glass, or polymer strips which are coated withsome type of adhesive (typically a pressure sensitive adhesive). Someembodiments of this type provide self-adherence, and are comprised of anSEBS formulation as described above for use in the fabrication ofreference channel devices.

[0058] Spacer wall devices are most preferably constructed to facilitateease of application to the working surfaces of the capillary. As shownin FIG. 8, for example, one specific embodiment is comprised of arectangular sheet, wherein a strip of material has been removed tocreate a rectangular void.

[0059] Such a construct allows the user to apply the device to theworking surfaces while the ends provide tabs which conveniently maintainspacing of the sidewalls during application and tabs for manualgripping. Following application, the closed ends of the resultantcapillary may be cut away to create a capillary appropriate forsubmersion in the test fluid.

[0060] Extensive investigation has shown that both reference channel andspacer wall embodiments are useful for a broad range of specificmeasurements and methods of analysis. Specifically, once a subjectsurface is incorporated within a capillary device, submersion of theresultant capillary, along its length, in an appropriate vessel, causesfluid to rise within the channel. The height of fluid within thecapillary following submersion (at a given time) may be utilized,through a variety of techniques, to deduce various subject surfacecharacteristics and parameters relating to the affinity of the testfluid for the surface (such as contact angle).

[0061] Given the illustrative theoretical analysis presented above, oneobvious method for analyzing surface characteristics from fluid heightmeasurements involves calculation of contact angle using theoreticalprinciples. As outlined above, the contact angle may be directly deducedfrom consideration of forces acting on the fluid column within thecapillary. In devices wherein one working surface of the capillarychannel is not the subject surface (as in a reference channel device),deduction of contact angle at the subject surface begins with adetermination of contact angle made between the test fluid and theworking surface of the channel. This may be accomplished through heightmeasurement in a capillary comprised of the reference channel in contactwith an identical test surface. The reference surface contact angle mayalso be deduced through analysis of results obtained from at least twomeasurements of fluid height using reference channels with differentdimensions or geometries. Once this contact angle has been determined,theoretical analysis allows determination of the contact angle betweenthe fluid and a given subject surface.

[0062] This method has been shown to allow deduction of the contactangle between a test fluid and a given surface, and thus, to allowcharacterization of various surface properties which are a function ofthis parameter. It is possible, for example, to rank the relativebondability, printability, and general affinity of a subject surface forother materials using contact angles, deduced through the methodsdescribed, against a given test fluid. In addition, it is found thatcontact angles thus calculated may be utilized to determine whethercontaminates are present on a given surface (the presence of oil orother organic contaminates on glass surfaces, for example, is easilydeduced from the contact angle thus obtained). Finally contact anglemeasurements, obtained through this method, are useful in determinationand characterization of surface roughness, through comparison of contactangles obtained for a given subject surface against that obtainedagainst a reference surface of known roughness or surface morphology.

[0063] Beyond direct computation of contact angles, another method forutilizing embodiments of the present invention involves comparativeanalysis of fluid height measurements as a means for characterization ofsurfaces. In this method, the height obtained using a given channeldevice is determined using a series of reference surfaces of knowncharacteristics. Comparison of the height obtained using a given subjectsurface is then compared to the reference values. In this manner,relative determination of printability, bondability, surface roughness,surface contamination, or any other aspect of surface physics related tocontact angle can be accomplished.

[0064] Finally, it is important to recognize that the above methods arenot only applicable in situations where static equilibrium has beenachieved, but also extend to situations involving dynamic contactangles. Of particular importance, it is possible to compute, or makerelative comparisons of, dynamic contact angles using the embodiments ofthe invention.

[0065] One particularly powerful method for analyzing dynamic contactangles using embodiments of the present invention involves the creationof an advancing or receding fluid height within the capillary. As shownin FIG. 9, this may be accomplished by submersion of the fluid in bathof fluid which, through pumping to add or remove fluid, is induced tochange level at a given rate. As a result, the fluid height within thecapillary will be induced to change at a specific rate. The height ofthe fluid within the capillary at a given instant, relative to themoving level of fluid in the bath, provides a measure of capillarypressure created by the dynamic contact angle in a manner exactlyanalogous to that presented above for the static situation. In somecases, a correction is needed for the pressure required to cause thefluid to flow into, or out of, the capillary as a result of viscousdrag. In any case, it will be obvious to one of ordinary skill in theart that such a method enables measurement of dynamic contact angles andrelated phenomena. Just as in the static case, either direct theoreticalanalysis, or relative comparisons can be undertaken.

[0066] It will further be obvious to one of ordinary skill in the artthat the creation of a dynamic fluid height within the capillary devicecan be accomplished though a variety of techniques. Specifically, thecapillary can be affixed to a stage which moves, along the capillarylength, into, or out of, a test fluid bath as shown in FIG. 10. Anymanner of similar techniques involving tipping or rotation of the bath,etc. may also be employed.

[0067] In order to measure the relative height of the fluid within thecapillary in such dynamic circumstances, it is possible to use anymanner of appropriate instrumentation and methodology. One of the mostpractical techniques involves time lapse video imaging of the capillaryduring a dynamic experiment coupled with either real time, orsubsequent, analysis to determine the relative height. In addition, moreadvanced methods for measurement and inference of the dynamic height,including but not limited to, resistance or impedance measurements offluid within the capillary and bath, acoustic measurements of height,and the like, may all be employed in this regard.

EXAMPLE 1

[0068] A reference channel device, with a rectangular channel crosssection, was fabricated using oil plasticized Kraton G 1650 SEBS rubber.

[0069] To enable the fabrication, a mold was machined out of a block of17-4 stainless steel alloy. This mold was rectangular, having a lengthof 8.000″, a width of 0.850″, and a depth of 2.000″. Along one of the8.000″×0.850″ faces of this mold, a raised step was created measuring0.015″ in height and 0.150″ in width. FIG. 11 shows a schematic drawingof the finished mold. This mold was highly polished, using fine diamondcompound, to achieve a mirror polish on the face with the raised step.

[0070] 10 grams of Kraton G 1650 polymer was measured into a sample cupalong with 1) 5 grams of Walnut Hill, Inc. general purpose andindustrial paraffin wax and 2) 85 grams of Lyondel Lubricants inc. DP500mineral oil. The resultant compound was thoroughly mixed and placed in aglass dish. This dish was then placed in a laboratory oven at atemperature of 175 degrees Celsius for 30 minutes. The material wasthoroughly stirred every 10 minutes during heating. This resulted in amolten liquor of sufficiently low viscosity to allow liquid casting of areference channel device.

[0071] The top of the mold was wrapped with PTFE pipe thread tape tocreate a dam approximately 0.1 inch high around the edge. The moltencompound was removed from the oven and immediately poured onto the mold(which was at ambient temperature). The thermoplastic elastomer castingwas allowed to cool for approximately 4 hours. The PTFE tape was peeledfrom the edge of the casting and the resultant rubber article wasremoved from the mold surface. This procedure produced a very soft,translucent rubber strip, approximately 8 inches in length, and 0.1inches in thickness, having a rectangular reference channel down thelength of one surface approximately 0.015 inches in depth by 0.150inches in width.

[0072] In order to verify the depth of this channel, and examine anydeformation which might occur when attached to a surface, a 2 inch stripof this material was cut from the casting and attached to the side of aflat-machined stainless steel surface. Using a Unitron toolmakersmicroscope, the opening of the capillary channel created against thesteel surface was observed from one end. Using the translationmicrometer to move the stage and measure the depth of the channel, thechannel depth was measured to be within 0.0002 inches of 0.015 inches.The channel depth, therefore, in all subsequent calculations, was takento be 0.015 inches.

[0073] In order to test this article, and compare differences in testfluid height within capillaries created against surfaces with differentproperties, various standard polymer films with differentcharacteristics were tested. A rectangular acrylic vessel, 4.00 inchesin height by 2.00 inches square, was thoroughly cleaned with HPLC gradedeionized water (GFS Chemicals, Inc. cat. # 1963 Stock # 76702). Aswatch was cut from the surface to be tested, and the surface wasadhered over the thermoplastic elastomer reference channel. In allcases, the natural tendency of the thermoplastic elastomer to form alight bond with the surface was used for adherence. A scale, marked inmillimeters, was affixed to the outside of the acrylic vessel and theassembled capillary was affixed to the inside the vessel, behind thescale, using the natural adherence of the unused side of thethermoplastic elastomer strip. A CCD camera was focused on the systemand the camera signal was input into a computer system allowing timelapse photography of the subsequent experiment. HPLC grade water at atemperature of 22 degrees Celsius was then poured quickly into thevessel to a predetermined height, bringing the water test fluid bathapproximately 1.5 inches above the bottom of the capillary channel.Using the computer, images of the system were digitally acquired at arate of 6 per minute.

[0074] Using this method, a series of different surfaces, having varyingaffinity for water, and general bondability/printability, were tested.The surfaces chosen were intended to cross a broad range of relatedeffects, and to encompass materials commonly tested and surface treatedto enhance bondability. In some cases, polymer surfaces were tested inboth a virgin non-treated state and following corona treatment providinga one to one demonstration of associated effects.

[0075] The specific surfaces tested were as follows:

[0076] 1) PTFE pipe thread tape (Webstone Inc., Worcester, Mass. #05262)

[0077] 2) Untreated High Density Polyethylene Film (Untreated side ofFilm Supplied by Griff Inc., Bristol, Pa. # 2147-03)

[0078] 3) Backside of a strip cut from the thermoplastic elastomercasting from which the reference channel device was cut

[0079] 4) Untreated Low Density Polyethylene Film (Untreated filmsupplied by Griff Incorporated # 1217-03.06)

[0080] 5) Corona Treated High Density Polyethylene Film (Treated side of15 mil film supplied by Griff Incorporated # 2147-03)

[0081] 6) Polyester Film (Untreated film supplied by Griff Incorporated# 1713-17*R)

[0082] 7) Flame treated glass microscope slide (free of organiccontaminates)

[0083] A sample of each of these surfaces was tested using the methodsoutlined above. Subsequently, the resulting digital time lapse video wasexamined in detail to determine the water height, relative to the bathlevel in the acrylic vessel, as a function of time.

[0084] In all cases, dynamics was observed over a period ofapproximately 120 seconds following submersion of the capillary openingby the water surface. Largely, a static equilibrium was observed beyondthis period extended up to observational limits of 1 hour.

[0085] The static fluid height, 120 seconds following submersion,measured relative to the water level in the bath, is listed for eachsurface tested in the table below (positive values are above the levelof the bath and negative values represent depression of the level withinthe capillary below the bath level). Material Height (1) −29.0 mm (2)−20.5 mm (3) −20.0 mm (4) −18.5 mm (5)  −8.0 mm (6)  −7.5 mm (7)  +8.0mm

[0086] Given these results, it is possible to measure differences incapillary fluid height which correlate to differences in affinity forother surfaces and correlate well to printability. As is well known,PTFE would be expected to display extreme hydrophobicity and lack ofaffinity for inks and other surfaces. Untreated HDPE and LDPE would beexpected to be less hydrophobic although sufficiently lacking inaffinity for other surfaces to present difficulties in printing andbonding. Corona treated HDPE would be expected to have greater affinityfor water and significantly improved printability and bondability.Polyester film is expected to display reasonable affinity for water andgood general printability and bondability. Finally, flame treated glasssurfaces are expected to have great affinity for water. Certainly, theseexact trends are displayed, with a high correlation of fluid height andgeneral expected affinity. In addition, it is obvious that relativecomparison of height measured for such surfaces could serve as a simplemethod for evaluation of bondability, printability, and the like.

[0087] Analytical estimation of contact angle between water and thesesurfaces was also undertaken. Given the width of the reference channelrelative to its depth, the effects of the fluid at the sidewalls of thechannel were ignored. Given this approximation, the contact anglebetween the thermoplastic elastomer and the water was calculated usingthe height obtained with the reference channel sealed over a surfacewith identical properties. From the theoretical analysis presentedabove, the contact angle was calculated using the expression

θ_(known)=cos⁻¹(ρghd/2y).

[0088] The density of water, ρ, was taken as 1.0 g/cc and the surfacetension of water at 22 degrees Celsius, was taken as 69.0 dyne/cm. Theacceleration due to gravity was taken to be 9.8 m/s². This yielded acontact angle estimate of 120 degrees.

[0089] Given θ_(known), the expression

θ_(unknown)=cos⁻¹(ρghd/y−cos(θ_(known)))

[0090] was used to estimate the contact angle between water and theother surfaces tested. In each case, θ_(known) was taken as 121 degrees,and the measured height was substituted into the expression. Thisyielded the following contact angle estimates: Water Contact MaterialAngle Estimate (1) 167° (2) 123° (3) 121° (4) 116° (5)  84° (6)  82° (7) 22°

[0091] As one of ordinary skill in the art will recognize, variousrefinements of these estimates are possible, but they serve to clearlyillustrate methodology for determining contact angles using embodimentsof the invention.

EXAMPLE 2

[0092] A second 2-inch long strip was cut from the thermoplasticelastomer casting described in Example 1 to create a second referencechannel device. This device was utilized in dynamic contact anglemeasurements.

[0093] The reference channel device was first attached to athermoplastic elastomer surface cut from the same casting such that allsurfaces within the resultant capillary were functionally identical. Theresultant capillary was adhered; through its natural adherence, to theinside of the same acrylic vessel utilized for the tests in example 1.The capillary channel was mounted vertically in juxtaposition to theexternal scale, marked in mm, mounted to the external surface of thevessel. A CCD camera system was focused on the capillary channel, andthe camera signal was output to a computer allowing time lapse videoimaging of the subsequent experiment.

[0094] A precision micro gear pump, with variable speed drive, was thenutilized to pump HPLC grade water into the acrylic vessel, at apredetermined and constant rate, as the computer recorded images of thesystem at a rate of 1 frame per second. As the water was pumped into thevessel at a fixed flow rate, the water bath level rose at a constantrate, ultimately, passing up the vertical exterior of the capillarydevice. As the water bath level rose, water was eventually forced torise within the capillary channel at some rate. The bath level wasallowed to rise until reaching the top of the capillary device, at whichtime the experiment was terminated. This procedure was repeated atdifferent rates of fluid flow into the -vessel, providing results atdifferent rates of fluid advancement within the capillary channel.

[0095] Subsequently, the time lapse video images of these experimentswere examined. At each flow rate, the difference in height between thesurface of the water in the bath, and the water rising within thecapillary channel, was measured as a function of time. In each case, itwas found that, following the onset of fluid flow up the capillarychannel, the height of fluid in the channel, relative to the bathsurface, quickly achieved a steady state which was maintained, withminor fluctuation, through the remainder of the experiment. Using thevideo images, the velocity of fluid front rising in the channel wasmeasured, following the achievement of steady state, along with thefluid height in the channel relative to the surface of the water in thebath.

[0096] The following table summarizes the results of these experiments:Height of Fluid in Fluid Front Velocity Channel (Rel. to Bath) 0.06mm/sec −21.0 mm 0.31 mm/min −21.0 mm 1.20 mm/sec −22.0 mm 1.90 mm/min−21.0 mm

[0097] Clearly, the fluid height in the channel, relative to the waterbath level, is little altered by the dynamics of the fluid within thecapillary. This result is important for several reasons. First, the lackof a significant change in height, relative to that obtained statically(an average of −21.25 mm vs.−20.0 from example 1), and as a function ofincreasing velocity, clearly indicates that the contact angle issubstantially unaltered by advancement over the surfaces of thisparticular thermoplastic elastomer formulation. In addition, it is clearthat viscous forces, required to cause the water to flow through thecapillary, may be ignored (since these forces are, obviously, too smallto influence the height measurement significantly under dynamicconditions).

[0098] From this data, it is appropriate to estimate that the contactangle between the water and the thermoplastic elastomer walls of thereference channel device, under the conditions given, is approximately123 degrees. In addition, it is appropriate to consider this contactangle unaltered by dynamic conditions.

[0099] Given this result, the reference channel device was attached toanother surface known to exhibit changes in contact angle as a functionof advancing or receding rate. This surface was that of anotherthermoplastic elastomer formulation sold commercially by GLScorporation. This material, Dynaflex G6708, was tested in tape form. Aswatch of the material was cut and attached to the reference channeldevice, to form a capillary which was adhered, exactly as above, to theinterior of the acrylic vessel.

[0100] Again, the micro-pump and video acquisition system were utilizedto measure the water height in the capillary, relative to the bathsurface, under steady state dynamic conditions as the fluid rose at aconstant rate within the capillary. This resulted in the following data:Height of Fluid in Fluid Front Velocity Channel (Rel. to Bath) 0.11mm/sec −16.0 mm 0.50 mm/sec −18.0 mm 1.35 mm/sec −22.0 mm

[0101] Here, the effect of the rate of advancement over the materialsurface is apparent.

[0102] Given this data, a wide range of analyses are possible.Underlying principles are illustrated through a simple approximateestimate of dynamic contact angle between water and the G6703 surface.Given the general lack of viscous effects, it is possible to ignore thepressures required for the fluid to flow into the capillary purely dueto hydrodynamic effects. With this assumption, the forces acting on thefluid column reduce to those already considered in the equilibriumanalysis presented in example 1. It is, therefore, appropriate toestimate the dynamic contact angle using the essentially unalteredrelationship

θ_(known)=cos⁻¹(ρghd/y−cos θ_(known)),

[0103] where θ_(known) is taken as 123°, and the same water parametersenumerated in example 1 are employed.

[0104] This analysis results in the following estimation of the dynamiccontact angle against Dynaflex G6708 thermoplastic elastomer surfaces,as a function of advancing fluid rate: Dynamic Contact Angle Fluid FrontVelocity Estimate 0.11 mm/sec 106° 0.50 mm/sec 112° 1.35 mm/sec 126°

[0105] Although such an analysis could incorporate a variety ofadditional effects, including viscous stresses created by fluid flow inthe capillary, and perturbations created at the capillary corners andside walls, this analysis provides estimates of dynamic contact anglegenerally representative of methods enabled by the invention.

[0106] These and other modifications and variations to the presentinvention may be practiced by those of ordinary skill in the art,without departing from the spirit and scope of the present invention,which is more particularly set forth in the appended claims. Inaddition, it should be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to limit theinvention so further described in such appended claims.

What is claimed is:
 1. A reference channel capillary device comprising:an open capillary channel embedded within a surface of a supportivematerials system, the capillary channel having a cross sectionalgeometry sufficient to create an open channel, the capillary devicebeing configured to form a closed capillary against an adjacent surface.2. A reference channel capillary device as defined in claim 1, whereinthe surface in which the open capillary channel is embedded isconfigured to adhere to an adjacent surface.
 3. A reference channelcapillary device as defined in claim 2, wherein the surface in which theopen capillary channel is embedded includes an adhesive coating.
 4. Areference channel capillary device as defined in claim 2, wherein thesupportive materials system comprises a polymer having adhesiveproperties that enables the surface of the supportive materials systemto adhere to an adjacent surface.
 5. A reference channel capillarydevice as defined in claim 1, wherein the open capillary channel isembedded within a planar surface.
 6. A reference channel capillarydevice as defined in claim 1, wherein the open capillary channel isembedded within a curved surface.
 7. A reference channel capillarydevice as defined in claim 1, wherein the open capillary channel isembedded within a planar surface and has a rectangular cross sectionwith a depth of less than about 0.020 inches and a width greater than 10times the depth.
 8. A reference channel capillary device as defined inclaim 1, wherein the supportive materials system is made from a polymer.9. A reference channel capillary device as defined in claim 1, whereinthe supportive materials system comprises glass.
 10. A reference channelcapillary device as defined in claim 1, wherein the supportive materialssystem comprises a ceramic material.
 11. A reference channel capillarydevice as defined in claim 1, wherein the supportive materials systemcomprises a metal.
 12. A reference channel capillary device as definedin claim 1, wherein the supportive materials system comprises asemiconductor.
 13. A reference channel capillary device as defined inclaim 1, wherein the supportive materials system comprises athermoplastic elastomer.
 14. A reference channel capillary device asdefined in claim 1, wherein the device is transparent or translucent.15. A reference channel capillary device as defined in claim 1, whereina surface of the capillary channel is coated with a layer of materialthrough electrodeposition, evaporation, sputtering, plasma treatment, orchemical vapor deposition.
 16. A reference channel capillary device asdefined in claim 1, wherein a surface of the capillary channel comprisesa polymer which is bonded to the supportive materials system.
 17. Areference channel capillary device as defined in claim 1, wherein thesupportive materials system is made from a material comprising a styreneethylene-butylene styrene block copolymer.
 18. A reference channelcapillary device as defined in claim 17, wherein the styreneethylene-butylene styrene block copolymer is mixed with a mineral oiland a paraffin wax.
 19. A reference channel capillary device comprising:an open capillary channel embedded within a supportive materials system,the capillary channel having a cross sectional geometry sufficient tocreate an open channel, the capillary device being configured to form aclosed capillary against an adjacent surface, the capillary devicefurther being configured to be placed against a curved adjacent surfacefor forming the closed capillary, the supportive materials system beingmade from a material comprising a polymer, a glass, a semiconductor, aceramic, a metal, a thermoplastic elastomer, or mixtures thereof.
 20. Areference channel capillary device as defined in claim 19, wherein thedevice is transparent or translucent.
 21. A reference channel capillarydevice as defined in claim 19, wherein a surface of the capillarychannel is coated with a layer of material through electrodeposition,evaporation, sputtering, plasma treatment, or chemical vapor deposition.22. A reference channel capillary device as defined in claim 19, whereina surface of the capillary channel comprises a polymer which is bondedto the supportive materials system.
 23. A reference channel capillarydevice comprising: an open capillary channel defined by a planar surfaceof a supportive materials system, the capillary device being configuredto form a closed capillary against an adjacent planar surface, thecapillary channel having a rectangular cross section with a depth ofless than about 0.02 inches and a width greater than about 10 times thedepth, the supportive materials system being made from a materialcomprising a polymer, a glass, a semiconductor, a ceramic, a metal, athermoplastic elastomer, or mixtures thereof.
 24. A reference channelcapillary device as defined in claim 23, wherein the device istransparent or translucent.
 25. A reference channel capillary device asdefined in claim 23, wherein a surface of the capillary channel iscoated with a layer of material through electrodeposition, evaporation,sputtering, plasma treatment, or chemical vapor deposition.
 26. Areference channel capillary device as defined in claim 23, wherein asurface of the capillary channel comprises a polymer which is bonded tothe supportive materials system.
 27. A spacer wall capillary devicecomprising a first spacer element spaced from a second spacer element,the spacer elements being configured to be attached to two opposingadjacent surfaces, the spacer elements holding the surfaces apartthereby producing a capillary.
 28. A spacer wall capillary device, asdefined in claim 27, wherein the spacer elements have a thickness ofless than about 0.020 inches.
 29. A spacer wall capillary device asdefined in claim 27, wherein the two spacer elements are initially heldsome distance apart by a support to facilitate application and creationof a capillary between parallel surfaces.
 30. A spacer wall capillarydevice as defined in claim 27, wherein the spacer elements are made froma material comprising sheets of a polymer, a metal, a ceramic, a glass,or a semiconductor.
 31. A spacer wall capillary device as defined inclaim 27, wherein the spacer elements comprise a thermoplasticelastomer.
 32. A method for analysis of surface properties comprising:providing a capillary device; placing the capillary device adjacent to asurface; contacting the capillary with a fluid; and measuring the heightto which the fluid rises in the capillary.
 33. A method for analysis ofsurface properties as defined in claim 32, wherein the height to whichthe fluid rises is utilized as a measure of surface printability.
 34. Amethod for analysis of surface properties as defined in claim 32,wherein the height to which the fluid rises is utilized as a measure ofsurface wettability.
 35. A method for analysis of surface properties asdefined in claim 32, wherein the height to which the fluid rises isutilized as a measure of bondability.
 36. A method for analysis ofsurface properties as defined in claim 32, wherein the height to whichthe fluid rises is utilized as a measure of surface affinity for othersubstances.
 37. A method for analysis of surface properties as definedin claim 32, wherein the height to which the fluid rises is utilized asa measure of surface contamination by foreign substances.
 38. A methodfor analysis of surface properties as defined in claim 32, wherein theheight to which the fluid rises is utilized as a measure of surfaceroughness.
 39. A method for analysis of surface properties as defined inclaim 32, wherein the height to which the fluid rises is utilized tocharacterize and identify surface coatings.
 40. A method for analysis ofsurface properties comprising: providing a capillary device; placing thecapillary device adjacent to a surface; contacting the capillary with afluid; measuring the height to which the fluid rises in the capillary;and determining a contact angle between the fluid and the surface fromthe amount the fluid rises in the capillary.
 41. A method for analysisof surface properties comprising: providing a capillary device;positioning the capillary device adjacent a surface to form a capillary;placing the capillary in a bath containing a fluid under dynamicconditions such that fluid flows into and out of the capillary due torelative motion of the capillary and the bath surface; and measuring theheight of fluid within the capillary relative to the level of fluid inthe bath.
 42. A method for analysis of surface properties, as defined inclaim 41, wherein the height of fluid within the capillary, relative tothe bath surface, is used to determine an advancing or receding contactangle.
 43. A method for analysis of surface properties as defined inclaim 41, wherein the height of fluid within the capillary, relative tothe bath surface is used as a relative measure of how the advancement orrecession of fluid over a given surface impacts fluid interaction withthe surface.
 44. A device for measurement of dynamic wetting effects ata surface comprising: a capillary device defining an open capillarychannel, the capillary device being configured to adhere to an adjacentsurface for forming a closed capillary against the surface; a referencebath for submersion of the closed capillary formed between the capillarydevice and the adjacent surface; means for causing recession oradvancement of a fluid within the capillary due to motion of thecapillary relative to a fluid bath surface; and means for measurement offluid height within the capillary relative to the fluid bath surface.45. A device for measurement of dynamic wetting effects at a surface asdefined in claim 44, wherein the capillary moves on a mechanical stage.46. A device for measurement of dynamic wetting effects at a surface asdefined in claim 44, wherein the fluid height in the bath is altered bycontrolled flow of fluid into, or out of, the bath.
 47. A device formeasurement of the dynamic wetting effects at a surface as defined inclaim 44, wherein the height of fluid within the capillary, relative tothe bath surface, is measured using video imaging.
 48. A device formeasurement of the dynamic wetting effects at a surface as defined inclaim 44, wherein the height of fluid within the capillary, relative tothe bath surface, is measured using a device that measures electricalresistance or impedance.
 49. A device for measurement of the dynamicwetting effects at a surface as defined in claim 44, wherein the heightof fluid within the capillary, relative to the bath surface, is measuredby an optical device.
 50. A device for measurement of the dynamicwetting effects at a surface as defined in claim 44, wherein the heightof fluid within the capillary, relative to the bath surface, is measuredacoustically by an acoustic device.
 51. A device for measurement of thedynamic wetting effects at a surface as defined in claim 45, wherein therate of motion of the mechanical stage is controlled by amicroprocessor.
 52. A device for measurement of the dynamic wettingeffects at a surface as defined in claim 46, wherein the height of fluidwithin the bath is controlled by a microprocessor.
 53. A device formeasurement of the dynamic wetting effects at a surface as defined inclaim 44, wherein the height of fluid within the capillary, relative tothe bath surface, is used to calculate dynamic contact angle.